(1) Field of the Invention
This invention relates to a proportional solenoid valve, and more particularly to a proportional solenoid valve having a valve lift thereof continuously changed in accordance with a value of an electric current supplied thereto.
(2) Description of the Related Art
In general, a proportional solenoid valve which has a valve lift thereof continuously changed by a solenoid force is comprised of a valve section for opening and closing a fluid passage by a valve seat and a valve element arranged in a manner opposed to the valve seat, and a solenoid section for actuating the valve element such that the valve element is moved to and moved away from the valve seat.
A conventional proportional solenoid valve has the component parts of a valve section and a solenoid section formed or mounted in a body formed by machining a block body. The valve section includes two ports bored in the block body, a valve seat integrally formed with the body at a location between the two ports, and a valve element opened and closed by the solenoid section. On the other hand, the solenoid section includes a solenoid coil to which an electric current is supplied from the outside, a core fixedly arranged on the same axis as the valve element and the valve seat and a plunger arranged such that it can move to and from the core in the axial direction to actuate the valve element, and a spring arranged between the plunger and the valve element, for urging the plunger in a direction away from the core.
In general, in the proportional solenoid valve constructed as above, since the valve element is arranged upstream or downstream of the valve seat with respect to flow of a fluid, and pressure applied to the valve element acts in the valve closing or valve opening direction, the characteristic of the valve lift with respect to a solenoid force is quite different depending on the direction of the fluid flow. For this reason, the proportional solenoid valve is given a directional property related to the fluid, and designed in a manner adapted to the direction of the fluid flow.
In the conventional proportional solenoid valve, however, the body in the form of a block is formed with the two ports, and has the component parts of the valve section and the solenoid section for opening and closing the valve element of the valve section, mounted therein, which causes an increase in the size of the proportional solenoid valve.
Further, when the proportional solenoid valve is applied to a location where the direction of the fluid flow is reversed, two pairs of a proportional solenoid valve and a check valve are required to be arranged in parallel such that the two pairs allow fluid to flow in respective directions opposite to each other, which causes an increase in the size of the proportional solenoid valve.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a small-sized and low-cost proportional solenoid valve which is capable of controlling bidirectional fluid flow.
To achieve the object, there is provided a proportional solenoid valve for changing a valve lift continuously according to a value of an electric current supplied to a solenoid coil. The proportional solenoid valve comprises a core fixed in a hollow cylindrical pipe, a partially hollow shaft having one end thereof fixed in the core axially of the pipe and another end thereof bored with a plurality of valve holes on a circumference thereof such that the bores communicate with a fluid passage extending axially of the pipe, a hollow cylindrical valve element arranged in a manner axially movable using the shaft as a guide so as to open and close the valve holes, a first spring arranged between the core and the hollow cylindrical valve element, for urging the hollow cylindrical valve element in a direction away from the core, a hollow cylindrical plunger fixedly fitted on the hollow cylindrical valve element, and a solenoid coil circumferentially provided on an outside of the pipe.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.